IMPROVE – Towards an IMPROVED framework for the ecological risk assessment of pesticide mixtures

Last changed: 20 June 2024
Rain drops on a water surface. Photo.

The beneficial effects of pesticides in crop production come along with the contamination of aquatic ecosystems.

Pesticides have positive effects on the yield of agricultural crops, but also lead to pollution in the aquatic environment. In order to minimise the risks associated with the use of these products, knowledge of the combination effects of pesticiedes is needed.

Pesticides used in agriculture also spread to water bodies. Concentrations in water can be particularly high during heavy rainfall and when the wind carries plant protection products during spraying. During these concentration peaks, animals and plants living in the aquatic environment are exposed. Since the products are designed to control pests and weeds, they are usually also toxic to animals living in the aquatic environment.

In Swedish environmental monitoring of pesticides, 10-12 products are usually found in a water sample from watercourses in the agricultural landscape. Data from other countries show similar results. These different substances can amplify or minimise each other's toxic effects. When authorising pesticides, these combination effects are not taken into account, but only the effects of single substances on a few standard organisms such as algae, crustaceans and fish. To measure the effects of pesticides at the same time, simplified addition models are used, which do not take into account synergistic effects between the substances. This is likely to underestimate the true toxicity of a mixture of PPPs.

The aim of IMPROVE was to deepen the knowledge of combination effects of plant protection products so that better risk assessments can be made. A key question addressed by the project was which combination of pesticides produce particularl combination effects.

IMPROVE contributed to a model that identifies combinations of pesticides with a particularly high risk to organisms and ecosystem processes (e.g. photosynthesis, decomposition of organic matter). The model was also tested within the project to quantify the effects.


Willem Goedkoop. Institutionen för vatten och miljö, SLU.

Maria Bighiu.  Institutionen för vatten och miljö, SLU.

Thomas Backhaus. Institutionen för biologi och miljövetenskap, Göteborgs universitet.


IMPROVE was funded by Formas - The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning.